In existing patient care systems, a standard personal computer (PC) (or other processing device) is typically interconnected with one or more medical devices. Such a PC typically needs to be rebuilt, or fabricated specially, so that the PC has electrical isolation at input and output connectors required in patient monitoring and/or therapy environments. In particular, four aspects of such electrical isolation are of importance.
Ground Integrity
When a patient is concurrently connected to more than one patient medical monitoring and/or therapy devices that are interconnected, and the medical monitoring and/or therapy devices are in conductive (e.g. metallic) housings or chassis, care needs to be taken that a difference in ground potential between the device enclosures does not cause current to flow through the patient in the accidental case that a patient touches or by some means comes concurrently into contact with both enclosures. For this reason electrical isolation is maintained between medical devices when concurrently connected to a patient.
Isolation of a device may be accomplished in one of different ways if the device has exposed metal parts. These ways include, for example:                1. The device housing is electrically isolated from the device electronics and individual input and output connectors are electrically isolated from the chassis ground connections; or        2. Power into the device is isolated from the exposed conductive part of the medical monitoring and/or therapy device, allowing the device chassis and input and output ports to float to one common potential.        
If the second method is used, the exposed housing of a medical device needs to satisfy a ground integrity test with respect to exposed housings of other interconnected medical devices in the system. Standards specify a limit of 200 milliohms (mohms) resistance between medical devices for such connections.
Power Sequencing
When “hot” plugging two connectors, i.e. plugging when the medical device is powered-on, it is desirable not to plug a pin coupled to a heavy electrical load into a socket which providing significant power or a spark may occur when plugging the connectors together. The spark may be small such as an ESD spark which has very high voltage but very little power behind it. In a powered system, however, a spark may occur even with a relatively low voltage if the power is large enough. In either case, a spark may be catastrophic in a patient environment which may include oxygen or other flammable or explosive gases or other materials.
Mechanical Latching
In order to ensure that the different medical monitoring and/or treatment devices do not accidentally become disconnected, once they are connected, connectors generally include mechanical latching. This prevents a potential difference from accidentally occurring between housings of two different medical devices concurrently connected to the patient. This also can prevent a spark from accidentally occurring when pins carrying power are separated.
Creepage Distance
Creepage refers to the conduction of electricity along the surface of a dielectric, and creepage distance is the shortest distance over the surface of an intervening dielectric between two conductors. Minimizing creepage reduces the resistance between conductors in a connector. One way to minimize creepage is to increase creepage distance between conductors in a connector.
Typically, providing the above electrical isolation requires a custom-built PC with electrical isolation built into each connector port and represents a complex and expensive implementation. A system according to invention principles addresses these needs and associated problems.